1. Technical Field
The present invention relates to a discharge lamp lighting device, a discharge lamp lighting method, and a projector device.
2. Related Art
In the past, there has been known a projector device equipped with a discharge lamp such as a high-pressure mercury lamp as a light source, and this type of projector device is provided with a resonant circuit for obtaining a high voltage for starting discharge of the discharge lamp (see JP-A-2007-27145 (Document 1)). According to this projector device, when lighting the discharge lamp, the high voltage is obtained by matching the frequency of the alternating-current power supplied to the discharge lamp with the resonant frequency of the resonant circuit. Further, after the discharge lamp starts discharge to light, the frequency of the alternating-current power supplied to the discharge lamp is lowered to thereby supply the discharge lamp with a voltage for stationary lighting.
Incidentally, individual difference and aging variation exist in the inductance component and the capacitance component of the resonant circuit. Therefore, if the frequency of the alternating-current power, which is supplied to the resonant circuit when lighting the discharge lamp, is fixed, there can occur the case in which the resonant fails to occur, and as a result, the discharge lamp fails to light. In order to avoid such a problem, according to the technology disclosed in Document 1, the frequency of the alternating-current power supplied to the discharge lamp is increased monotonically toward the resonant frequency to thereby find out the actual resonant frequency in every lighting operation (see description in, e.g., paragraphs 0076, 0081 of Document 1).
However, according to the related art described above of monotonically varying the frequency of the alternating-current power supplied to the discharge lamp, the resonant circuit is left in a quasi-resonant state until the discharge lamp starts lighting. In such a state, the voltage and the current in the resonant circuit increase, and further, the switching loss in, for example, a bridge circuit for generating the alternating-current power supplied to the resonant circuit also increases. Therefore, according to the related art described above, there arises a problem that the power consumption when lighting the discharge lamp increases.